There are a number of devices which use materials having non-linear electrical response (hereinafter non-linear material) for overvoltage protection. These devices use non-linear material comprising finely divided particles dispersed in an organic resin or insulating medium. The material is placed between contacts and responds or switches at predetermined voltages. U.S. Pat. No. 4,977,357 is directed to such a material which can be placed between and in contact with spaced conductors to provide a non-linear resistance therebetween; the material comprises a matrix comprised of a binder and closely spaced conductive particles uniformly dispersed in the binder. U.S. Pat. No. 4,726,991 is directed to a switching material which provides electrical overstress protection against electrical transients, the material being formed of a matrix comprising separate particles of conductive materials and semi-conductive materials, all bound in an inorganic insulating binder to form the switching matrix. U.S. Pat. No. 3,685,026 describes a switching device employing a non-linear material. In all such devices, the matrix has been applied between electrodes by forming the matrix material into the space between the electrodes, by applying a coating of the material to one electrode and then applying the second electrode, or by extruding, rolling/calendaring, pressing or molding the material into a thin sheet which is then sandwiched between electrodes. In all such methods, it is difficult to precisely achieve the desired thickness of the non-linear material and to provide intimate contact with the associated electrodes.
There is a need to provide an overvoltage protection element which can be integrated into connectors or electronic circuits at a lower cost than the use of discrete services such as clamping diodes. There is also a need for such a device which can be used in connection with multiple lines and which has low capacitance compared with diodes, thereby providing less interference with transmitted electrical signals.